I have a hollow alloy tube, 200mm long and 20mm diameter and 5mm thickness. There is a set force at the top end trying to snap it in 2. Somewhere in about the middle of the rod I need to have a small cutout section in the outer diameter of about 2 mm deep. If the length of this cut out is 2mm long or 20mm long will this make any difference to the strength of the rod.

NielBasic MemberPosts:193

10 Sep 2012 02:02 PM

The simple answer to your question is yes. You have changed the moment of inertia of the tube with this cut.

To evaluate how much you are reduced the strength you need to analyze the resulting beam.

Niel Leon engineering.com

johnson290159New MemberPosts:2

11 Sep 2012 07:44 PM

Thanks Neil,

So the length of the thinner cut out section will determine the overall strength of the tube.

The shorter the cut out section, the less leverage on that thinner area, is that correct ??

Thanks again

NielBasic MemberPosts:193

14 Sep 2012 01:04 PM

Johnson:

Yes, the thinned area will effect the overall strength of the tube. The change will be proportional to the reduction in moment of inertia.

The length of the cut out has little effect on the reduction in strength. It is the change in moment of inertia that is important.